1. Field of the Invention
The present invention relates to image processing method and apparatus for analyzing characteristics of image data of each pixel.
2. Related Background Art
Conventional methods of forming retrieval keywords in an electronic file system consist of mainly the following two methods.
(I) Method in which image data is read from an image input apparatus such as a scanner or the like and the operator manually inputs a retrieval keyword.
(II) Method of reading the image data from an image input apparatus such as a scanner or the like, recognizing a character image in an original image, and automatically adding a retrieval keyword.
Although the method of (I) is a certain method and the retrieval keyword can be set independent of the input image, the operator needs to add the keyword every time and it is troublesome from a viewpoint of the operation.
According to the method of (II), since the characters in the image are recognized and are automatically added for retrieval, the operation is simple.
The method of (II), however, has the following problems.
That is, an image in which only character portions are extracted, namely, which is binarized by what is called an optimal threshold process is preferable as an image for the character recognition, so that it is undesirable to execute a halftone process even to an image in which original image includes a halftone image. Therefore, a case such that the portion of the halftone image perfectly becomes black or white and the contents of the image in such an area cannot be recognized occurs.
On the other hand, an image processed so as to relatively accurately conform to the original image is requested as an image to be displayed or recorded.
Therefore, the image binarized by the optimal fixed threshold is necessary for character recognition and the image which was halftone processed is necessary to display/record. The image suitable for the character recognition isn't always suitable for the image to display/record, and vice versa.